Investigations of fuel cell electrochemistry: Ab initio studies of electrocatalytic transformations

David Ingram, Adam Holewinski, and Suljo Linic

Fig. 1, Schematic of a solid oxide fuel cell (SOFC), which comprises a Nickel anode, Yttria-stabilized Zirconia (YSZ) electrolyte, and Lanthanum Strontium Manganite (LSM) cathode.
Fig. 2, (Left) Free-energy diagram for electro-oxidation of hydrogen over Ni(211) evaluated at 800°C and 1 atm under three cell operating potentials. (Right) Gibbs free energies for Ni(211), Co(211), and Cu(211) surfaces at various cell operating potentials [Mukherjee 2007].

Solid Oxide Fuel Cells

Solid oxide fuel cells convert the chemical energy of hydrocarbon fuels into electricity by electrochemical oxidation of the fuel. The promise of high conversion efficiency makes SOFC technology a lucrative option for efficient usage of fossil fuels. Although SOFC technology has been evolving over the past few decades, not much is known about elementary electrochemical mechanisms that govern their performance. In this project we use Density Functional Theory (DFT) and statistical thermodynamics to investigate the underlying molecular mechanisms that govern the electrochemical oxidation of hydrogen and methane over different metal and ceramic SOFC anodes. The thermodynamic and kinetic information thus derived provides insights into the thermodynamic limitations and kinetic barriers associated with different mechanisms. This forms the basis for a bottom-up formulation of better anode electrocatalysts for SOFCs.

Low Temperature Fuel Cells

An important hurdle in the development of low-temperature fuel cell technologies is that the Pt anode, aside from being very expensive, poisons rapidly in the presence of small quantities of carbon monoxide (CO). It has been shown that alloying Pt with other metals such us Ru, Sn, and others alleviates this problem. Two mechanisms have been proposed to explain the improved CO tolerance of bimetallic catalysts:

Metal atoms alter the electron structure of nearby Pt atoms, making binding of CO to Pt less favorable.
Metal atoms promote oxidation of CO to CO₂.

We utilize a hybrid computational-experimental approach, combining first principles calculations with ultra-high vacuum (UHV) experiments to study the mechanism by which the additive metals improve the CO tolerance of Pt electrodes.

Related Group Publications

Joydeep Mukherjee and Suljo Linic, “First principles investigations of electrochemical oxidation of hydrogen at solid oxide fuel cell operating conditions”, Journal of the Electrochemical Society, 154(9), B919-B924,
2007.

Upcoming Presentations

Oral Presentations

David Ingram and Suljo Linic, “First Principles Studies of Electrochemical Reactions at Solid Oxide Fuel Cell (SOFC) Electrodes”, AIChE Annual Meeting, Catalysis & Reaction Engineering Section, November 16–21, 2008, Philadelphia, PA.

Poster Presentations

David Ingram and Suljo Linic, “Electrochemistry from First Principles: Studies of Electrochemical Transformations at Model Solid Oxide Fuel Cell (SOFC) Anodes”, AIChE Annual Meeting, Catalysis & Reaction Engineering Section, November 16–21, 2008, Philadelphia, PA.

Previous Presentations

Oral Presentations

David Ingram, Joydeep Mukherjee, and Suljo Linic, “First principles studies of electrochemical oxidation reactions at model solid oxide fuel cell (SOFC) anodes”, ACS National Meeting, April 6–10, 2008, New Orleans, LA.

Poster Presentations

David Ingram and Suljo Linic, “Electrochemistry from First Principles: Studies of Electrochemical Transformations at Model Solid Oxide Fuel Cell (SOFC) Anodes”, Gordon Research Conference on Catalysis, June 22–27, 2008, Colby-Sawyer College, New London, NH.
David Ingram and Suljo Linic, “Electrochemistry from First Principles: Studies of Electrochemical Transformations at Model Solid Oxide Fuel Cell (SOFC) Anodes”, MCS Annual Symposium, May 8, 2008, General Motors Research & Development Center, Warren, MI.


	Projects Publications Laboratory Investigations of fuel cell electrochemistry: Ab initio studies of electrocatalytic transformations David Ingram, Adam Holewinski, and Suljo Linic Fig. 1, Schematic of a solid oxide fuel cell (SOFC), which comprises a Nickel anode, Yttria-stabilized Zirconia (YSZ) electrolyte, and Lanthanum Strontium Manganite (LSM) cathode. Fig. 2, (Left) Free-energy diagram for electro-oxidation of hydrogen over Ni(211) evaluated at 800°C and 1 atm under three cell operating potentials. (Right) Gibbs free energies for Ni(211), Co(211), and Cu(211) surfaces at various cell operating potentials [Mukherjee 2007]. Solid Oxide Fuel Cells Solid oxide fuel cells convert the chemical energy of hydrocarbon fuels into electricity by electrochemical oxidation of the fuel. The promise of high conversion efficiency makes SOFC technology a lucrative option for efficient usage of fossil fuels. Although SOFC technology has been evolving over the past few decades, not much is known about elementary electrochemical mechanisms that govern their performance. In this project we use Density Functional Theory (DFT) and statistical thermodynamics to investigate the underlying molecular mechanisms that govern the electrochemical oxidation of hydrogen and methane over different metal and ceramic SOFC anodes. The thermodynamic and kinetic information thus derived provides insights into the thermodynamic limitations and kinetic barriers associated with different mechanisms. This forms the basis for a bottom-up formulation of better anode electrocatalysts for SOFCs. Low Temperature Fuel Cells An important hurdle in the development of low-temperature fuel cell technologies is that the Pt anode, aside from being very expensive, poisons rapidly in the presence of small quantities of carbon monoxide (CO). It has been shown that alloying Pt with other metals such us Ru, Sn, and others alleviates this problem. Two mechanisms have been proposed to explain the improved CO tolerance of bimetallic catalysts: Metal atoms alter the electron structure of nearby Pt atoms, making binding of CO to Pt less favorable. Metal atoms promote oxidation of CO to CO₂. We utilize a hybrid computational-experimental approach, combining first principles calculations with ultra-high vacuum (UHV) experiments to study the mechanism by which the additive metals improve the CO tolerance of Pt electrodes. Related Group Publications Joydeep Mukherjee and Suljo Linic, “First principles investigations of electrochemical oxidation of hydrogen at solid oxide fuel cell operating conditions”, Journal of the Electrochemical Society, 154(9), B919-B924, 2007. Upcoming Presentations Oral Presentations David Ingram and Suljo Linic, “First Principles Studies of Electrochemical Reactions at Solid Oxide Fuel Cell (SOFC) Electrodes”, AIChE Annual Meeting, Catalysis & Reaction Engineering Section, November 16–21, 2008, Philadelphia, PA. Poster Presentations David Ingram and Suljo Linic, “Electrochemistry from First Principles: Studies of Electrochemical Transformations at Model Solid Oxide Fuel Cell (SOFC) Anodes”, AIChE Annual Meeting, Catalysis & Reaction Engineering Section, November 16–21, 2008, Philadelphia, PA. Previous Presentations Oral Presentations David Ingram, Joydeep Mukherjee, and Suljo Linic, “First principles studies of electrochemical oxidation reactions at model solid oxide fuel cell (SOFC) anodes”, ACS National Meeting, April 6–10, 2008, New Orleans, LA. Poster Presentations David Ingram and Suljo Linic, “Electrochemistry from First Principles: Studies of Electrochemical Transformations at Model Solid Oxide Fuel Cell (SOFC) Anodes”, Gordon Research Conference on Catalysis, June 22–27, 2008, Colby-Sawyer College, New London, NH. David Ingram and Suljo Linic, “Electrochemistry from First Principles: Studies of Electrochemical Transformations at Model Solid Oxide Fuel Cell (SOFC) Anodes”, MCS Annual Symposium, May 8, 2008, General Motors Research & Development Center, Warren, MI.